The present invention relates to a rotary compressor of the sliding vane type and, more particularly, to a sliding vane type rotary compressor suitable for use as the compressor of a refrigerator incorporated in an air conditioning system for vehicles.
The sliding vane type rotary compressor has a small number of parts and is small-sized and of simple construction. Thanks to these advantages, the sliding vane type rotary compressor now has a spreading use as the refrigerating compressor for automobile air conditioning systems, in place of the conventional reciprocating compressors.
The sliding vane type compressor, however, has the following disadvantage as compared with the reciprocating compressors.
The sliding vane type rotary compressor for an automobile air conditioning system is adapted to be driven by the engine of the automobile through a belt which goes round a pulley coupled to a clutch connected to the rotary shaft of the compressor. Therefore, the refrigerating power of the air conditioning system incorporating the sliding vane type rotary compressor is increased substantially linearly in proportion to the increase of the engine speed.
In contrast, in the conventional reciprocating compressor, the suction valve cannot well follow-up the operation of the compressor when the operating speed is increased to a high level, so that the efficiency of the suction of refrigerant gas into the compressor is decreased to cause a saturation of the refrigerating power. In other words, in the case of the reciprocating compressor, the refrigerating power is automatically suppressed during high-speed running of the automobile. In the case of the rotary type compressor, however, such an automatic suppressing effect cannot be obtained so that the efficiency is lowered in accordance with the increment of the compression work or a state of overcooling occurs as the engine speed is increased.
In order to obviate the above-described problem of the prior art, it has been proposed to provide a control valve in the passage leading to the suction port of the rotary compressor adapted to vary the opening area in such a manner that the opening area is decreased as the engine speed is increased to cause some suction loss to automatically control the refrigerating power. This solution, however, is not preferred because the construction is complicated and the production cost is raised due to the provision of the control valve.
As another countermeasure for overcoming the problem of excessive refrigerating power, it has been proposed to use a fluid clutch, planetary gear or the like to drive the rotary compressor in such a manner that the speed of the compressor is not increased beyond a predetermined limit speed.
The use of the fluid clutch, however, poses a problem of a large energy loss due to generation of heat by friction-loss inherent to the clutch itself. Also, the use of the planetary gear mechanism, which is inevitably accompanied by an increase of the number of parts and increase of the size of the driving unit, is impractical in view of the current demand for simple and compact construction to meet the requirement for saving of energy.